feat: replace mail protocol with smolmail and rebuild the UI

lib/presentation/widgets/small_loading_spinner.dart

@@ -1,17 +1,17 @@
 import "package:flutter/material.dart";
 
 class SmallLoadingSpinner extends StatelessWidget {
-  const SmallLoadingSpinner({Key? key}) : super(key: key);
+  const SmallLoadingSpinner({super.key});
 
   @override
   Widget build(BuildContext context) {
-    return const SizedBox(
+    return SizedBox(
       width: 20,
       height: 20,
       child: Center(
         child: CircularProgressIndicator(
           strokeWidth: 2,
-          color: Colors.white,
+          color: Theme.of(context).colorScheme.onPrimary,
         ),
       ),
     );